Patent Literature 1 (JP 2007-203307A) discloses a riveting machine which joins joined materials. The riveting machine controls a pushing quantity of a rivet into the joined material based on the board thicknesses of the joined materials. Thus, the surface of the rivet and the surface of the joined material are made flat.
FIG. 1 shows a fastened work 300 fastened with a fastener 420 and a nut 440. The fastener 420 contains a countersunk bolt. The fastened work 300 contains stacked composite material parts 351 and 352. A countersink through-hole 300a is formed in the fastened work 300 to pass from a surface 300b on the one side to a surface 300c on the other side. A countersink portion of the countersink through-hole 300a is arranged on the side of the surface 300b. The method of fastening the fastened work 300 contains disposing the fastener 420 to the countersink through-hole 300a and attaching the nut 440 to the fastener 420. Here, a smoothness B300 as a distance from the surface 300b to the head surface 421a of the fastener 420 in a direction of the countersink through-hole 300a is managed within a predetermined range. The smoothness B300 shows a recess or a protrusion of the head surface 421a from the surface 300b. 
In recent years, a case where a composite material part such as fiber reinforced plastics is used instead of a metal part has increased. For example, many composite material parts have been used for an aircraft. When manufacturing the aircraft, the management of smoothness is especially important for the purpose of the reduction of air resistance.